1. Field of the Invention
The present invention relates to a method of manufacturing a piezoelectric device, and more particularly, to a method of manufacturing a piezoelectric device including a piezoelectric substrate that is bonded to another substrate.
2. Description of the Related Art
A circuit section of a wireless communication device, such as a cellular phone, for example, requires an interstage filter and a duplexer. Piezoelectric devices have been used in interstage filters and duplexers in the past. Examples of the piezoelectric devices include elastic wave devices, such as a surface acoustic wave (SAW) device and a boundary acoustic wave device, bulk acoustic wave (BAW) devices, film bulk acoustic resonators (FBAR), and other suitable devices. These piezoelectric devices include a piezoelectric substrate.
An example of a known piezoelectric device is described, for example, in Japanese Unexamined Patent Application Publication No. 2008-546207. As shown in FIG. 5, in Japanese Unexamined Patent Application Publication No. 2008-546207, comb-shaped electrodes 113 and 123 are provided on a first piezoelectric substrate 111 and a second piezoelectric substrate 121, respectively. The first piezoelectric substrate 111 and the second piezoelectric substrate 121 are connected to one another by a joining member 131 such that the comb-shaped electrodes 113 and 123 face each other. The comb-shaped electrodes 113 and 123 are electrically connected to connection electrodes 112 and 122, respectively. The connection electrodes 112 and 122 are electrically connected to each other. A through-hole 124 is arranged to extend through the second piezoelectric substrate 121 to electrically connect the connection electrode 122 to a surface electrode 133.
Heretofore, piezoelectric devices including a piezoelectric substrate that is bonded to another substrate in order to adjust the temperature characteristic of the resonant frequency have been known. When a bonded structure is applied to the structure of Japanese Unexamined Patent Application Publication No. 2008-546207, a through-hole must be provided through the structure having the bonded structure. Depending upon the method used to form the through-hole, problems such as the time required to create the through hole or the generation of microcracks have been observed.